Since in laminated glass, an object is hard to penetrate when the laminated glass is subjected to an external impact and even though it is broken by the object, fragments of broken glass seldom shatter and therefore it is safe, laminated glass is widely employed in the windowpanes of vehicles such as automobiles, aircrafts, buildings and the like. As laminated glass of this kind, there is widely used laminated glass obtained by bonding an interlayer for laminated glass, which comprises an adhesive resin, for example, a plasticized polyvinyl acetal resin such as a polyvinyl butyral resin plasticized with a plasticizer, between transparent glass plates.
The laminated glass using the above conventional interlayer for laminated glass has high safety, however, it has low heat ray shielding property. Among light rays, infrared rays, having a wavelength of about 780 nm or more which is longer than that of visible light, have a smaller energy quantity than ultraviolet rays by about 10%, however, they have a large thermal effect, and when they are absorbed in a substance once, they are released in the form of heat and result in a temperature rise, and therefore they are generally referred to as heat rays.
Thus, if it becomes possible to shield infrared rays (heat rays), having a large thermal effect, of light rays entering from windshields and side glass of automobiles, the heat ray shielding property is enhanced and a temperature rise of the interior of automobile can be inhibited. As a recent trend, an opening area of windowpanes in automobiles, buildings and the like increases and the necessity of enhancing the heat ray shielding property of the laminated glass and of imparting the heat ray shielding function to opening areas of these windowpanes increases.
By the way, in Patent Document No. 1, there is disclosed an interlayer for laminated glass obtainable by dispersing heat ray shielding fine particles such as indium tin oxide fine particles and antimony-doped tin oxide fine particles having a heat ray shielding property, in an adhesive resin such as plasticized polyvinyl acetal resins, and laminated glass using this interlayer for laminated glass. Such an interlayer for laminated glass and laminated glass have a high heat ray shielding property and also an excellent transparency and are very useful for windowpanes of automobiles, buildings and the like.
But, in such an interlayer for laminated glass and laminated glass having a heat ray shielding property, since the heat ray shielding fine particles dispersed in the interlayer shield visible light in a red color region due to its property and scatter visible light in a blue color region depending on their particle diameter, the resulting transmitted light shows yellow-greenish color tone, and the interlayer for laminated glass and the laminated glass to be obtained take on slightly yellow-greenish color. Therefore, when the concentration of the heat ray shielding fine particles is increased in order to attain a highly heat ray shielding property, a degree of yellow-green color tone is increased. Thus, since in applications requiring a transparent property which looks a natural color, it is impossible to enhance the concentration of the heat ray shielding fine particles, this method is not yet adequately satisfactory for the purpose of attaining a highly heat ray shielding property in a transparent condition and has the problem to be improved in this point. Patent Document No. 1: WO 01/25162